Communication systems including high-speed transceivers are used to communicate data between devices. The data rate requirements of such communication systems continue to increase as technology advances. As a signal is transmitted, an encoding scheme for symbols in the signal may be employed. An example of an encoding scheme is a 2-level PAM (PAM-2) scheme, which is also referred to as a non-return-to-zero (NRZ) scheme. For the NRZ scheme, the signal may include two possible discrete pulse amplitudes. A transmit symbol may have one of two different values (e.g., with normalized amplitude levels of +1 and −1), which may be represented using a single bit. As data rates increase to meet demand for higher data throughput, multi-bit symbols based on various encoding schemes (e.g., PAM-N, where N is an integer greater than two) may be used. For the PAM-4 scheme, the signal may include four possible discrete pulse amplitudes, and a transmit symbol may have one of four different values (e.g., with normalized amplitude levels of −3, −1, +1, and +3), which may be represented using two bits. While using multi-bit symbols based on encoding schemes such as PAM-4 may increase data rates and bandwidth efficiency, testing and measuring PAM-N signals including multi-bit symbols may be challenging and expensive.
Accordingly, it would be desirable and useful to provide an improved way of characterizing devices that transmit multi-bit symbols based on encoding schemes such as PAM-4.